From 1e2a516e89fc412a754327522ab271b42f99c6b4 Mon Sep 17 00:00:00 2001 From: Balbir Singh Date: Thu, 29 Jun 2017 21:57:26 +1000 Subject: [PATCH] powerpc/kexec: Fix radix to hash kexec due to IAMR/AMOR This patch fixes a crash seen while doing a kexec from radix mode to hash mode. Key 0 is special in hash and used in the RPN by default, we set the key values to 0 today. In radix mode key 0 is used to control supervisor<->user access. In hash key 0 is used by default, so the first instruction after the switch causes a crash on kexec. Commit 3b10d0095a1e ("powerpc/mm/radix: Prevent kernel execution of user space") introduced the setting of IAMR and AMOR values to prevent execution of user mode instructions from supervisor mode. We need to clean up these SPR's on kexec. Fixes: 3b10d0095a1e ("powerpc/mm/radix: Prevent kernel execution of user space") Cc: stable@vger.kernel.org # v4.10+ Reported-by: Benjamin Herrenschmidt Signed-off-by: Balbir Singh Signed-off-by: Michael Ellerman --- arch/powerpc/kernel/misc_64.S | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/arch/powerpc/kernel/misc_64.S b/arch/powerpc/kernel/misc_64.S index c119044..8ac0bd2 100644 --- a/arch/powerpc/kernel/misc_64.S +++ b/arch/powerpc/kernel/misc_64.S @@ -614,6 +614,18 @@ _GLOBAL(kexec_sequence) li r0,0 std r0,16(r1) +BEGIN_FTR_SECTION + /* + * This is the best time to turn AMR/IAMR off. + * key 0 is used in radix for supervisor<->user + * protection, but on hash key 0 is reserved + * ideally we want to enter with a clean state. + * NOTE, we rely on r0 being 0 from above. + */ + mtspr SPRN_IAMR,r0 + mtspr SPRN_AMOR,r0 +END_FTR_SECTION_IFSET(CPU_FTR_ARCH_300) + /* save regs for local vars on new stack. * yes, we won't go back, but ... */ -- 2.7.4